Mouse embryos containing two paternal (biparental andogenones) and two maternal (biparental gynogenones) pronuclei do not complete development but die soon after implantation. Preimplantation development of such embryos appears morphologically normal. Androgenetic embryos display failure of development of the embryo proper while gynogenones fail because of poor growth and/or differentiation of extraembryonic membranes. The overall objective of this proposal is to analyze the interactions of cells from gynogenones, androgenones and normal embryos in aggregation chimeras, thus determining whether cell lethality or failure of morphogenetic interactions is responsible for developmental failure. We propose to construct aggregation chimeras using various combinations of androgenetic, gynogenetic and normal blastomeres. Subsequent development of such embryos will be monitored and participation of each component determined. In order to determine the exact derivation of each cell in such chimeric embryos, in situ identification methods will be used. We propose to use embryos from transgenic mouse lines already developed in our laboratory. Foreign DNA sequences will be detected in nucleus of each cell by in situ DNA hybridization using biotinylated probes. Since each cell derived from transgenic embryos carries specific detectable sequences, the origin and contribution of each component of the chimeric embryo can be easily determined. By comparing spatial and quantitative distribution of gynogenetic, androgenetic and normal cells within embryos with the developmental capacity of various chimeric embryos we will determine the role of paternal and maternal genome in early morphogenetic events during mouse development.